Summary: Functions

Key points

• Functions can be defined using the function declaration, or by creating a function expression by assigning an anonymous function to a variable.
• Arrow functions are a shorthand notation that can used for writing short, one-line, anonymous functions.
• All functions return a value. If this isn’t explicitly stated, the function will return undefined.
• A parameter is a value that’s written in the parentheses of a function declaration and can be used like a variable inside the function’s body.
• An argument is a value that’s provided to a function when it’s called.
• The return value of a function can be assigned to a variable.
• A callback is a function that’s provided as an argument to another function and can be called from within the body of that function.

Functions are a really important part of any programming language. But so are “objects”—which we’ll be learning about after the quiz and challenge!